Its better to put the column name along with values to track the errors.and also if you put column name with values then if in future there is a need to add one more column in that database table, then the existing query will not get affected.

So by using qry1 method of writing query will help you to identify the missing values.and if say one more column as column5 added to table_name then the qry1 will work with out error, where as qry2 will give error as Column count doesn't match value count.

in above query NULL refers to first column for the table DBPrefix.$user->user_data['id'] refers to second column of the table DBPrefix.$system->cleanvars($_SESSION['SELL_title']) refers to the third column of the table DBPrefix.and so on.

so in this way you can identify the column names to the respective value.